A municipal well that was part of a network to determine ambient water-quality across Iowa. All sampling took place as close to the wellhead as possible--prior to any treatment (e.g., chlorination). Water samples were representative of the aquifer (raw water), not what people were necessarily drinking.

The logistics for sampling groundwater for pesticides can get quite complicated. Great care is taken to prevent contamination of samples.

Dye was used in a study of atrazine (a herbicide) degradation on Roberts Creek, Iowa, to determine the transport time of water as it moves through the study reach of the stream. The red color in the stream is rhodamine WT dye.

Downstream view of Roberts Creek, Iowa, where USGS scientists conducted a study of the degradation of atrazine (a herbicide) in streams.